1. Field of the Invention
This invention relates to a heat recovery type combustion apparatus which is configured to utilize the heat of exhaust gas arising from combustion for heating the air to be used for combustion.
2. Description of the Prior Art
In the combustion apparatuses which are used in such industry grade furnaces as forging furnaces, normalizing furnaces, and refining furnaces and such steam-generation purpose heating apparatus for turbines, the heat recovery type combustion apparatuses which are configured to utilize the heat of exhaust gas emanating from combustion for heating the air to be used for the combustion have been enjoying prevalent acceptance.
The recuperator which is used in these combustion apparatuses is generally provided with a specific heat exchanger interposed between an exhaust gas line and a combustion air line which are closely disposed to each other and, therefore,, is enabled to exchange heat between the air and the exhaust gas flowing through the two lines and utilize the heat of the exhaust gas resulting from combustion for heating the air to be used for the combustion. The heat which is recovered by means of this recuperator is about 50% in point of temperature level. In the case of an industry grade furnace which gives rise to exhaust gas of a temperature of 1,200 C., for example, the combustion air which has exchanged heat with the exhaust gas has a temperature of about 600 C.
The recupterator is heavily restricted in point of not only material for the construction thereof but also space for the installation thereof. It possibly occupies more floor space than the main body of a furnace or a heating apparatus.
Recently, the present inventor has proposed a combustion apparatus (Japanese Unexamined Patent Publication No. 222,102/1989) which is configured as illustrated in FIGS. 9 and 10.
This combustion apparatus 100 is provided with a burner 112 for heating a substance W subjected to the heating inside the main body R of a furnace. In the wall of the furnace near the burner 112 is disposed a regenerative member 122 made of an air-pervious ceramic material, with a cylindrical shape and to be partitioned to the pattern of a honeycomb. This regeverative member 122 absorbs the heat of the hot exhaust gas when this exhaust gas is discharged from within the main body R and allows this heat for heating the combustion air which is passing through an air conduit 119. The supply of the heat to the combustion air is continued by causing the regeverative member 122 by a motor M through the medium of a rotary shaft 123.
However, since this combustion apparatus 100 must rotate the regeverative member 122 exposed to the interior of the main body R which is destined to rise to a high temperature, it is required either to interpose between the rotary shaft 123 and the motor M heat-insulating means capable of intercepting the heat transmitted from the regeverative member 122 via the rotary shaft 123 to the motor M or to set the motor M at a position so distant as to disrupt the thermal effect of the regeverative member 122. The provision of these means adds to the size of the combustion apparatus 100 or complicates the whole configuration thereof.
Further, the regeverative member 122 of this combustion apparatus 100 remains at an elevated temperature while in service and at a low temperature while out of service and alternates expansion and shrinkage in spite of the ceramic material thereof. When the regeverative member made of the ceramic material which alternates expansion and shrinkage as described above must be rotated, it is allowed a desired increase in size only with difficulty. A combustion apparatus with a large capacity for combustion which consumes the combustion air and discharges the exhaust gas both in huge volumes, therefore, is not easily attained.
Further, the regeverative apparatus which alternates expansion and shrinkage and, at the same time, rotates renders it difficult to set the burner in place at the center thereof. It, therefore, has the disadvantage in that the burner and the air conduit are separated from each other, the flexibility with which the size, sharpness, etc. of a flame emitted from the burner are controlled is degraded, and the capacity for control or versatility dwindles. Though various electrical control devices may be used for the purpose of improving the controllability of the burner, for example, the use of these devices is not desirable because they increase the cost of the apparatus as a whole.